Dustfall Rate Research Articles

Dust deposition at the Mars Pathfinder landing site: observations and modeling of visible/near-infrared spectra

Temporal variations in the visible/near-infrared reflectance spectra of the radiometric calibration targets on the Mars Pathfinder (MPF) lander obtained by the Imager for Mars Pathfinder (IMP) camera reveal the effects of aeolian dust deposition at the MPF site throughout the mission. Sky brightness models in combination with two-layer radiative transfer models were used with these data to track changes in dust opacity on the radiometric calibration targets (RCTs) to constrain the dust deposition rate and the spectral properties of the deposited dust. Two-layer models were run assuming both linear and nonlinear dust accumulation rates, and suggest that RCT dust optical depth at the end of the 83-sol mission was 0.08 to 0.16, or on the order of 5- to 10-μm thickness for plausible values for dust porosity and grain size. These values correspond to dust fall rates of about 20–45 μm per Earth year, consistent with previous studies of dust deposition on Mars. The single scattering albedos of the dust derived from the models fall between those previously determined for atmospheric dust and bright soils. Comparisons of relative reflectance spectra calibrated using observed RCT radiances from late in the mission versus using radiances from modeled (dust-free) RCTs also reveal distinct spectral differences consistent with dust on the RCTs. Temporal variations in RCT dust opacity are not clearly linked to known passages of vortices at the MPF site, but overall suggest that deposition of dust onto the targets by local dust devils may be favored over erosion. Analyses of temporal changes in visible/near-infrared spectra will provide valuable information for future missions by constraining how dust deposition affects landed spacecraft operability (e.g., solar power availability), instrument calibration, and interpretations of surface mineralogy and composition.

Pedoecological effects of a sand-fixing poplar ( Populus simonii Carr.) forest in a desertified sandy land of Inner Mongolia, China

To assess the pedoecological effects of a 23-year old poplar (Populus simonii Carr.) forest on soil amelioration and vegetation restoration via soil erosion reduction and atmospheric dust retention in a desertified sandy land ecosystem, daily dynamics of wind speed, sand transport and dust deposition rates were monitored over an erosive period from April through June in 2001, using fixed observation sites located at different positions within and around the forest. Soil and vegetation characteristics at these sites were also measured. The observation sites were placed at distances of 15H (as control), 6H and 3H (H is mean tree height) from the forest edge of the windward side (abbreviated CK, 6H-W and 3H-W respectively), forest center (FC), and at distances of 0H, 6H and 8H from the forest edge of the leeward side (FE-L, 6H-L and 8H-L respectively). Daily mean wind speed was significantly lower in different observation sites than CK, with FC having the greatest reduction of wind speed and 6H-W the least reduction. Daily transport rate of sand by wind was also significantly lower in different observation sites than CK, with FE-L having the greatest reduction of wind erosion and 6H-W the least reduction. The fact that the poplar forest will lose its functions against wind at a distance of about 12-fold tree height from the forest edge of the leeward side suggests that the effective wind-preventing range of the poplar forest is about 150 m. There was marked spatial and seasonal distribution of dust-fall rate. Over space, the rate of dust-fall was much greater within the forest than outside the forest. Over time, the daily dust deposition rate was greatest in April, followed in decreasing order by May, June, July, September and August, closely linked to the seasonal distribution pattern of dust storm. Significant positive changes in soil and vegetation parameters of the different observation sites during the 23 years that the poplar forest was established suggest the perceptible pedoecological effects of the poplar forest on soil development and restorative succession of plant community within its immediate vicinity through windbreak, soil erosion reduction and atmospheric dust retention. Understanding these pedoecological effects may aid in the design of protective forest systems in arid and semi-arid areas.

Assessment of the palaeoclimate during 3.0–2.6 Ma registered by transition of Red Clay to loess–palaeosol sequence in central North China

A continuously accumulated section (the Yanyu section) of Red Clay and loess–palaeosol sequence from the southernmost Chinese Loess Plateau was selected for this study of palaeoclimate of the late Pliocene to early Pleistocene period. Termination of the Red Clay accumulation and onset of loess deposition was coincident with the beginning of extensive Northern Hemisphere glaciation at 2.6 Ma. Field observations and compositional analyses suggest an aeolian origin for the Red Clay, much like the processes experienced by the loess–palaeosol sequence. Pedogenic analysis indicates that the late Pliocene Red Clay first experienced complete decalcification and illuviation (mechanical translocation of clays) in all horizons, including the present carbonate precipitation zones, but other chemical alterations have been rather weak and even weaker than experienced by the overlying loess-derived palaeosols. In great contrast to the Pleistocene climate characterised by frequent and large-amplitude fluctuations between cold–dry and warm–wet, a relatively steady warm–dry climate condition is implied for the late Pliocene. Dustfall rate assessment indicates a much lower accumulation rate during the late Pliocene than in the early Pleistocene, in agreement with a notable systematic coarsening from the Red Clay to the overlying loess and palaeosols. Together, these features suggest that the dust transport agent, the northwesterly winds, were weaker over the late Pliocene. The transition from Red Clay to loess possibly marked a significant and rapid shift in the climatic system in east Asia.

Changes in soil characteristics around coal-fired power plants

The impact of coal-fired power plant emissions on certain physical and chemical properties of the soil was studied. A significant increase in bulk density and a decrease in porosity were observed at the sites receiving higher pollution than the control site. Soil pH was mostly alkaline at the polluted sites. The organic carbon content of the soil increased with increasing pollution load. Thermal power plant emissions have led to significant increases in the soil sulphate sulphur and exchangeable calcium contents, while reducing significantly total nitrogen. Reduction in total-N was positively correlated with the N-mineralization rate. The changes in total and organic sulphur, exchangeable potassium, and available phosphorus contents of soil were not significant. Significant positive correlations were found between dust fall rate and exchangeable Ca 2+ and K + contents of the soil and between ambient SO 2 concentrations and soil SO 4 2--S contents. The values of trace elements such as Mn, Fe, Cd Cu, Pb, and Ni were higher at sites closer to thermal power plants.

Frequency of cleaning the surface of photovoltaic cells in the environment of Riyadh City, Saudi Arabia

SYNOPSIS The effect of accumulation of atmospheric dust particles onto the surface of photovoltaic cells has been examined, and the permissible reduction in the power output was determined along with the associated dust deposition density. The annual patterns of dustfall over six different districts in the City of Riyadh which were previously measured by the author have been used to determine dustfall dependence for three groups of months over the year. A method for determining the frequency of cleaning the surface of photovoltaic cells is presented and used to determine the periods between cleaning during each group of months. The determination of such periods is based on the dust deposition density which would result in the maximum allowable power output reduction and the rate of dustfall during each group of months.

A study of spatial distribution of air pollutants in some coal mining areas of Raniganj coalfield, India

Ambient air quality monitoring for suspended particulate matter, sulphur dioxide, and nitrogen oxides was carried out over a period of one year to study diurnal and seasonal variations and spatial distribution of said pollutants. Dustfall rate measurements were carried out for a period of one month out of each season and for all the four seasons of the year. Studies were also carried out at selected work places to determine levels of the above-mentioned pollutants. Studies indicate that mining and associated activities have raised the background levels of particulate pollution in the region. The coal handling plant and poorly maintained roads, resulting in transport of coal dust by means of wind, are identified as the sources of particulate pollution in a coal mining area. Coal burning and transportation activities appear to be major sources of SO 2 and NO x in coal mining areas.

Technogenic pollution of the snow cover on Svalbard

Abstract Quantitative aspects of technogenic pollution of the snow cover are reported, based on field measurements made in the vicinity of the Barentsburg coalmine, Spitsbergen, in 1987. The mean total contamination of the snow cover with solid aerosols, based on cores through the total depth of the snow pack, reached levels of 300 t/ km2 for the immediate area of the settlement of Barentsburg and 30 t/km2 for the surrounding area. The rate of dustfall within the settlement is estimated to be 480 t/ km2 per year. The total amount of dust falling throughout the area of contamination which is 6 times larger than that of the settlement per se reaches 6001 per year. The data recorded on pollution of the snow cover at Barentsburg are comparable with those from the Vorkuta coalmining region. It is concluded that the pollution is local in nature. The importance of studies of snow pollution within the framework of a wider program of environmental protection of the archipelago of Svalbard is demonstrated.

Airborne dust fall on the California Channel Islands, U.S.A.

A thin, light-colored, silt-rich deposit covers soils of various ages on the California Channel Islands. The widespread distribution of this layer and data on its particle size distribution, particle morphology and mineralogy suggest that it is of aeolian origin. Examination of Landsat imagery indicates that the main source for aeolian dust is the western Mojave Desert when easterly Santa Ana winds prevail several times each year. Dust fall rates on San Clemente Island are in the range of about 28–31 g/m2/year and may reflect accelerated erosion of soil surfaces disturbed recently by human activity in the Mojave Desert.

Air pollution in the semitropical Saudi urban area

This paper presents the outcome of research conducted in the city of Jeddah, Saudi Arabia. Analysis of recorded meteorological elements shows that the atmosphere of the area favors the accumulation of air pollutants. Dustfall rates were measured at 22 stations in different districts. High rates of dustfall were found in all districts, with maximum recorded values in central urban and industrial districts. Collected samples were analyzed to determine the causes of these excessive precipitations. Suspended particulate matter and other pollutants were found to exceed air quality standards set to meet environmental requirements. Carbon monoxide was found to exceed the air quality standard of 9 μL/L. Concentrations of photochemical oxidants indicated the possibility of Los Angeles-type photochemical smog formation. Geographic distribution of pollutant concentrations and chemical constituents of particulates were found to be influenced by both manmade and natural causes. Results are discussed and several conclusions are given.

Visual response to dustiness.

Dustiness is a visually perceived phenomenon. In this paper, results of a quantification experiment for dustiness using a photometric method of measuring dust deposition and panel sampling techniques are reported. It was found that with maximum contrast a 0.2% effective area coverage (EAC) by dust can be perceived against a clean background. The minimum perceivable difference between varying gradations of shading was a change of 0.45% EAC. The results also revealed that a dust deposition level of 0.7% EAC was required before the object so covered was deemed unfit to use. A telephone survey indicated that the minimum tolerable interval between household dusting was every four days. Combination of the telephone survey information with the level of dust coverage found to be objectionable implies that a dustfall rate of less than 0.17% EAC/day would be tolerable for the population at large.

Recommended Standard Method for Continuing Dust Fall Survey (APM-1, Revision 1)

The suggested standard method of dust fall collection, as set forth in the following sections, is presented in an effort to promote a uniform approach to measurement of rate of dust fall

Dustfall as a Source of Water Quality Impairment

An investigation was made of dustfall during the months of June, July, and August, 1964, in Seattle, Wash., and surrounding areas to determine the possible effects of dustfall on reservoir water quality. Several components of dustfall were measured at 46 stations located within Seattle and its suburbs. The methods of sampling and analysis are described. The dustfall rates and their significance in terms of water quality, source, and meteorological factors are examined.

Dispersal of Dust Particles from Elevated Sources

The equations of Sutton for the atmospheric diffusion of gaseous pollutants are extended to the case of particles of appreciable free falling velocity with the boundary condition that dust fall rate equals ground level concentration times free falling velocity. It is shown that the effect of gravitational settling can be allowed for by (a) substituting the height above ground of the downward deflected plume axis for chimney height and (b) by introducing a factor a(x,z) as a multiplier to the "reflection" term in Sutton's equation.